Out-of-sync olm sessions

[richvdh]

I've seen pairs of android devices failing to communicate with

E/MXOlmDevice: ## decryptMessage() : decryptMessage failed BAD_MESSAGE_MAC

[richvdh]

See, for example, https://github.com/matrix-org/riot-android-rageshakes/issues/133 and https://github.com/matrix-org/riot-android-rageshakes/issues/132.

See also https://github.com/matrix-org/riot-android-rageshakes/issues/123, which may be due to corruption on the android end, or may not.

It's possible these were hangovers from #799, but at this point it seems somewhat unlikely.

[richvdh]

Hopefully yannick fixed this in matrix-org/matrix-android-sdk@aa5016b

[richvdh]

For the record: under certain conditions it was possible for two instances of MXFileCryptoStore to be active at once; the old one was used to encrypt a message while the new one was still loading; then when the old instance was discarded, the state had been rewound.

[ylecollen]

fixed with b6fecb7

[richvdh]

Note to self: The symptoms of this bug in the logs are something like the following.

Normal start for MXFileCryptiStore is as follows:

05-24 17:51:23.692 1633 D/MXFileCryptoStore: ## preloadCryptoData() starts
05-24 17:51:23.703 1633 D/MXFileCryptoStore: ## preloadCryptoData() : load mOlmAccount in 11 ms
05-24 17:51:23.705 1633 D/MXFileCryptoStore: ## preloadCryptoData() : load mRoomsAlgorithms (0 algos) in 0 ms
05-24 17:51:27.863 1633 D/MXFileCryptoStore: ## preloadCryptoData() : load 889 olmsessions in 4158 ms
05-24 17:51:41.772 1633 D/MXFileCryptoStore: ## preloadCryptoData() : load 1991 inboundGroupSessions in 13904 ms

(note the significant pauses while it loads the olm sessions and inboundgroupsessions).

When this bug happens, it looks more like:

05-08 13:04:27.681 786 D/MXFileCryptoStore: ## preloadCryptoData() starts
05-08 13:04:27.691 786 D/MXFileCryptoStore: ## preloadCryptoData() : load mOlmAccount in 10 ms
05-08 13:04:27.692 786 D/MXFileCryptoStore: ## preloadCryptoData() : load mRoomsAlgorithms (0 algos) in 0 ms
... lots of other things, including other operations on MXFileCryptoStore
05-08 13:04:30.426 786 D/MXFileCryptoStore: ## preloadCryptoData() : load 726 olmsessions in 2733 ms
... more other things.
05-08 13:04:46.932 786 D/MXFileCryptoStore: ## preloadCryptoData() : load 3169 inboundGroupSessions in 16505 ms